Quantifying the Rainy Season in the Brazilian Northeast Through a Modification of the Relative Entropy Method

In this work, we introduce a modification of the relative entropy method in order to perform geographically explicit quantification of the rainy season across the Brazilian Northeast (NE). We apply this novel approach to data from the ERA5-Land project for the period 1980 to 2022, with ~9 km spatial resolution, to obtain the strength of seasonality, the duration of the rainy season (in months), and the center of the rainy season, throughout the NE, both on the ERA5-Land grid and at municipality level. Our results agree well with the results of a number of other publications for several municipalities and regions within the NE. We also provide user-friendly software with graphical user interface for ease of extraction of rainy season parameters (strength, duration, and the center of the rainy season), together with the monthly precipitation series for any point or municipality average.